One of the internet's most ubiquitous sites, Wikipedia, is facing a shortage of new volunteers that threatens its future growth.

The not-for-profit Wikimedia Foundation, which runs Wikipedia and its related sites, says its group of web pages is the fifth most visited in the world, accessed by around half-a-billion people last year.

Wikimedia says it is the only not-for-profit running a top 40 global website, so you would think money would be its biggest problem.

However, the foundation's 2011-12 financial report shows it received donations and contributions of more than $US35 million, with almost another million worth of donated equipment.

When I read Wikipedia I find lots missing and I think that there's lots of new material that wants to be added to Wikipedia.

Wikimedia executive director Sue Gardner

Its total cash expenditure was around $US27 million, leaving it a handy surplus.

Wikimedia's executive director Sue Gardner, in Australia for a speaking tour, says Wikimedia is now pulling in around $US40 million a year in donations from its users, up from around a million when she joined the organisation in 2007.

"I actually think that charities tend to exaggerate the effects of those kinds of economic crisis on their revenues," she told ABC News Online.

"People can be finding themselves really in desperate circumstances, but that's a small proportion of the population, most people are belt tightening a little bit in hard times and they're not going to cut out small charitable contributions that matter to them, because frankly it feels good to give to charity."

Volunteer decline

Instead, Sue Gardner says it is a fall in the number of new people volunteering to edit articles and administer the site that is the biggest concern.

"We don't know how serious of a concern that should be," she said.

"There's a school of thought which suggests that after you've written the article about Saturn and accounting and France, that you don't need as many editors as you used to - once you have a solid base of articles inside Wikipedia, really at that point you're just making small improvements and you're just keeping things up to date.

"I don't know if that's true or not - when I read Wikipedia I find lots missing and I think that there's lots of new material that wants to be added to Wikipedia that's not there yet."

Sue Gardner says the foundation's ultimate goal would be for everyone to be a Wikipedia editor, to meet its aim to be repository for the sum of human knowledge.

While that holy grail is likely unachievable, she says the foundation is working to make Wikipedia easier to edit for non-geeks.

"It's a little too hard to contribute right now... you have to learn Wiki syntax, which is not hard to learn but it takes a little time," she observed.

"We're rolling out what we call the visual editor this [northern hemisphere] summer, and that's going to make it significantly easier to edit... and so, at that point, we expect that one of the big impediments will come down and we'll be able to have a more generalist editor base."

Wikipedia is also recruiting new editors through partnerships with universities, where lecturers give students a page to write or update as part of their coursework.

Developing nation push

The major new frontier for the foundation is an effort to give more people in developing countries access to Wikipedia, particularly those whose only access to the worldwide web is through their mobile phone.

It is doing this by partnering with mobile phone providers who agree to waive the data charges for visiting Wikipedia's mobile site on their networks.

However, Wikipedia says the arrangements are non-exclusive and non-commercial, with no money changing hands and the Wikipedia site remaining ad free.

"I think that they [the phone companies] feel like it's a service to their subscribers and so maybe their subscriber would be more likely to go with them as a provider than some alternative company that doesn't offer that," Sue Gardner explained.

"They want to be understood to be a good, responsible corporate citizen, and probably a little bit of it may not be entirely rational, but I think they like Wikipedia too."

You can listen to the full interview with Sue Gardner here, where she also discusses Wikipedia's competition, the reliability of its information, and how fingertip access to facts and figures is changing the way we think.